acclimatisation:

adventitious: developing from unusual points of origin, such as shoots or roots from callus or from leaf explants, or embryos from other sources than a zygote

androgenesis: senso stricto it means development from an anther; it is however most often used in a more restricted sense to indicate one obtained haploids or doubled haploids from these anthers

anther culture: culture of anthers in tissue culture

aneuploidy: the situation which exists when the nucleus of a cell does not contain an exact multiple of the haploid number of chromosomes

antioxidant: product which is preferably oxidised; mainly used in case of browning problems to avoid or to minimise the formation of polyphenolics

artificial seed: encapsulated somatic embryo

asepsis: without infection, avoiding contamination

autoclaving: the use of pressurised steam to sterilise ustensils and devices used in tissue culture

autotrophy: if an organism does not require a particular essential growth substrate or cofactor to be added exogenously

axenic: free from association with any foreign form of life (cannot been proven as we do not have appropriated tools)

axillary buds: formed in the axil of a leaf

bacteria free: the use of this term should be avoided and be replaced by "tested for a particular bacteria" (we do not have the adeqauate diagnostic tools at our disposal to prove cultures are completely bacteria free)

batch culture: discontinuous way of growing cell suspensions in a closed system in which the amount of nutrients becomes limiting as the growth progresses

binary vectors: the use of two compatible plasmids for genetic engeneering; one of them is a broad host-range vector containing the T-DNA border regions flanking selective markers and other foreign genes, the second plasmid carries the virulence genes (often called the helper plasmid) but has a large deletion in the T-DNA region

biotransformation: a process through which the functional groups of organic compounds are modified by living cells

browning: refers to colour change of medium or explant: most often associated with the formation of polyphenolics (melanines, quinones)

callogenesis: de novo formation of callus

callus: unorganised growth of cells, does occur in nature for healing wounds, does occur in tissue culture as a proliferative mass of differentiated cells

caulogenesis: de novo formation of buds

cell culture: the maintenance or cultivation of cells in vitro, including the culture of single cells; the cells are no longer organised into tissues

cell hybridisation: the fusion of two or more dissimilar cells leading to the formation of a synkaryon

cell suspension: culture of cells in a suspension; most often it is not really isolated cells but aggregates of up to 10 cells

cellulase: cellulose-degrading enzyme

chimera: in a chimeral plant not all the cells have the same genetic information; a distinction is made between sectorial, mericlinal and periclinal ones; such plants cannot be micropropagated by adventitious bud formation

clonal propagation: asexual propagation of plants that are considered to be genetically uniform and originated from a single individual or explant; a synonym for clonal propagation in vitro is micropropagation

clone: genetically identical organisms

competence: the possibility to manifest totipotentiality

conditioned medium: culture medium that has supported growth of cells; such a medium will contain a range of cell-derived molecules (e.g. amino acids, growth substances) that may enhance the growth of a subsequent batch of cells

contaminant: unwanted organism invading cultures; differs from a pathogen in the sense that a contaminant is not necessarily responsible for diseases

convection:

cryopreservation: ultra low temperature storage of cells, tissues, organs or seeds; it is usually carried out at temperatures below -100⁰C, as in liquid nitrogen (-196⁰C)

cybrid: cytoplasmic hybrid, viable cell containing cytoplasts from two different origins and the nucleus from one of them

de-differentiation: loss of specialised function, usually characterised by small isodiametric cells

differentiation: acquisition of specialised cell functions; the differentiated status is usually stable and in plant tissue culture the term is often taken to indicate the formation of shoots, roots or even other organs

diffusion:

dihaploid: having the number of chromosomes of the gametes of a plant which was originally a tetraploid

disinfectants: different products used to decontaminate plant material

double layer system: culture system where instead of subculturing a liquid medium is poured on top of the existing culture

electrofusion: fusion of protoplasts held in an appropriate electric field

electroporation: creation of transient pores in the plasmalemma, by means of an electrical current, for the purpose of introducing exogenous material, specially DNA, from the medium

elicitor: compound, often of pathogen origin, that can influence enzymes in biosynthetic pathways leading to increased or altered accumulation of secondary metabolites

embryo culture: culture of an isolated embryo from zygotic origin

embryogenesis: de novo formation of somatic embryos; syn. adventitious or asexual embryogenesis

embryoid: embryolike structure formed under in vitro conditions, this structure has the potential for further development into a plantlet

epigenetic: selective gene expression, any change in phenotype which does not result from an alteration in DNA sequence; is inheritable in the sense that there is no transmission of the change to meiotic progeny but is heritable in the sense that it can be passed from one cell generation to the next; an example is switching off of genes by base methylation

euploid: the situation which exists when the nucleus of a cell contains an exact multiple of the haploid number of chromosomes

evocator: product or environment that will enhance specific symptoms under certain conditions

explant: tissue or organ taken from its original site and transferred to an artificial medium for growth or maintenance

feeder culture:

friability: a term indicating the tendency for plant cells to separate from one another

gametoclone:

genetic variation: when the new characteristic can be passed sexually

genetic engineering: use of a vector (e.g. a plamid) or mechanical devices (shot gun) to transfer genetic information (DNA)

genotype: plants with the same genetic information (DNA)

haploid: having a single set of chromosomes

hardening: application of mild environmental stress to prepare the plant for more rigorous growing conditions

head space: gaseous environment of a tissue culture container

heterokaryon: a cell possessing two or more genetically different nuclei in a common cytoplasm, usually as the result from cell to cell fusion

homokaryon: a cell possessing two or more genetically identical nuclei in a common cytoplasm, usually as the result from cell to cell fusion

hyperhydricity: physiological abnormality occuring in tissue culture; formerly the word vitrification was used

hypersensitivity reactions: upon wounding a cell will initiate its defence mechanisms, thereby influencing the neighbouring cells; phenolics are involved in this type of reactions and are quite often related to the browning problem

induction: initiation of a structure, organ or process

inoculum: tissues or organs taken from an established tissue culture and transferred to fresh medium for subculture

in vitro: literally it means under glass, to indicate cultures were kept in glass containers under aseptic conditions; glass can now eventually be replaced by plastic

in vivo: normal growing conditions (e.g. in a garden or a greenhouse)

isogenic lines:

juvenility: conceptual term to indicate the status of a plant that has not yet flowered and from which cuttings can easily be rooted

meristem culture: culture of a shoot apical meristem in view of avoiding contaminations, especially specific viruses and bacteria

micropropagation: term often used to indicate large scale clonal propagation

mixotrophy: an essential substrate for growth is partly provided exogenously and partly by the plant; often used to characterise the origin of carbon sources in a plant, part is provided by the carbon source in the culture medium and part by the photosynthetic activity of the plant in culture

morphogenesis: (a) the evolution of a structure from an undifferentiated to a differentiated state; (b) the process of development and of growth of differentiated structures

mother plant: plant from which a tissue culture is initiated

nurse culture:

organogenesis: de novo formation of organs (caulogenesis, embryogenesis, rhizogenesis)

packed cell volume: the volume of cells present at any time during the growth cycle

pectinase: an enzyme that hydrolyses pectin, a heterogeneous polysaccharide mainly found in the middle lamella between adjacent cell walls. Incubation of tissue with pectinase can produce individual, walled cells

permeability:

phenotype: physical appearance; visual perception of the interplay between the genotype and the environment

phytoalexin: a non-specific antibiotic substance produced by plant cells in response to infection by pathogens, or environmental stress or injury; it isoften phenolic substances

plasmolysis: the removal of water from a cell, with attendant shrinkage, resulting from hyperosmotic extracellular conditions

polarity:

primary metabolite: essential metabolites (e.g. carbohydrates, proteins, lipids), components of the essential metabolic pathways

propagules: units that can be considered for in vitro propation purposes

protoplast = cell - cell wall

protoplast fusion: technique in which protoplasts are fused into a single cell

regeneration: term used in plant cultures to indicate a morphogenic response that results in the neoformation of organs (roots, buds, embryos, ..)

rhizogenesis: de novo formation of roots

secondary metabolite: a metabolite that is not part of the primary metabolic network of the cells. Primary metabolites are components of fundamental biochemical pathways (e.g. glycolysis) that are present in all cells. Secondary metabolites only appear in cells that are specialised in some way e.g. in defence

shoot apical meristem: undifferentiated tissue, located within the shoot tip, generally appearing as a shiny dome-like structure distal from the youngest leaf primordia and measuring less than 0.1 mm in length when excised

somaclonal variation: genotypic or phenotypic variations occuring in tissue culture, the latter being either genetic or epigenetic in origin

somatic embryogenesis: see embryogenesis

somatic hybrid: the cell or plant resulting from the fusion of plant protoplasts (nuclear fusion must have taken place), respectively derived from somatic cells which differ genetically

stage 0: a step in in vitro propagation of plants, aiming to prepare the plant material for successful introduction in tissue culture

stage I: a step in in vitro propagation of plants characterised by the establishment of an aseptic culture

stage II: a step in in vitro propagation of plants characterised by the rapid numerical increase of propagules

stage III: a step in in vitro propagation of plants characterised by preparation of the propagules for successful transfer to soil, a process which can involve hardening off, elongation, rooting

stage IV: a step in in vitro propagation characterised by the establishment in soil of a tissue culture derived plant, in certain cases stage IV can follow stage II

sterilisation: sterile = without life; sterilisation are the procedures used to kill all germs

subculture: transfer of a part of a developed culture to fresh culture medium

suspension culture: a type of culture in which cells, or aggregates of cells, multiply while suspended in liquid medium

synkaryon: a hybrid cell which results from the fusion of the nuclei it carries

tissue culture: abbreviation for protoplast, cell, tissue, organ and plant culture under in vitro conditions

totipotentiality: a cell characteristic in which the potential for forming all the cell types in the adult organism is retained, theoretically it means that each cell can give rise to a complete plant (vs competence)

transgenic: possessing genes from a different organism

transformation: in plant cell culture it is used for the introduction and stable genomic integration of foreign DNA into a plant cell, resulting in a genetic modification

undifferentiated: not specialised, see dedifferentiation

vitrification: formation of amorphous ice during the process of cryopreservation; formerly also used to describe the process of hyperhydricity

virus free: the use of this term should be avoided and replaced by virus indexed (for a specific virus); the reason is that we cannot prove something is virus free